My 40 plus years in the painting, drywall and all kinds of challenging home repairs have always led to solutions that may not appear on a product label.Painting over a wallpapered surface can be a successful project. Removing wallpaper can be a messy task and can create more work than necessary. My process that works is: I inspect the wallpaper for any loose seams or bubbles. I remove the edges by tearing off the loose edges until the area comes to a sound area. I cut out the bubbles with a razor knife being careful to just remove the bubbled areas. The next step is to prime the entire wallpapered surface with an oil base primer. I have used some water based primers with success it I always test them first to see if the wallpaper or teared off areas cause the paper to loosen or bubble. Kilz 3 is one of late that I have used with success after testing. After the primers has thoroughly dried I apply joint compound over the vertical seams and areas where the loose seams and bubbles were removed I start with a 6 inch broad knife on the first coat. Let dry. I skim the second coat of compound with a 8 or 10 inch and fish with a 14 inch kinfe on the final coat. I do not sand between coats, only scraping lightly with a broad knife to remove any raise edges. After I am pleased with the compound being smooth I sand lightly or use a very damp cloth wrapped around a sanding sponge block to eliminate drywall dust. The damp cloth and sanding block is a little tricky but once you get results without all the dust it's worth it. Once all the area are dry and smooth I like to prime the wall with a best quality drywall primer and follow up with my finish coat of first quality. Sounds like a lot of steps but each one goes quickly and eliminates the big mess of removing wallpaper and repairing gouged out places that scrapers have made. An additional step that I do is that I caulk the perimeter edges and corners with a good siliconized latex caulk or use a product called Grab made by Loctite. This is my Tested Tried & True method of painting over wallpaper.